abstract
The reaction mechanisms of CO, and its isoelectronic molecules OCS and CS2 dissolved in N-butyl-N-methylpyrrolidinium acetate and in 1-butyl-3-methylimidazolium acetate were investigated by DFT calculations in "gas phase". The analysis of predicted multistep pathways allowed calculating energies of reaction and energy barriers of the processes. The major role played by the acetate anion in the degradation of the solutes CS2 and OCS as well as in the capture of OCS and CO, by the imidazolium ring is highlighted. In both ionic liquids, this anion governs the conversion of CS2 into OCS and of OCS into CO, through interatomic S-O exchanges between the anion and the solutes with formation of thioacetate anions. In imidazolium acetate, the selective capture of CS2 and OCS by the imidazolium ring competes with the S-O exchanges. From the calculated values of, the energy barriers a basicity scale of the anions is proposed. The C-13 NMR chemical shifts of the predicted adducts were calculated and agree well with the experimental observations. It is-argued that the scenario issued from the calculated, pathways is shown qualitatively to be independent from the functionals and basis set used, constitute a valuable tool in the understanding of chemical reactions taking place in liquid phase.
keywords
GAS-PHASE; 1-BUTYL-3-METHYLIMIDAZOLIUM ACETATE; DENSITY FUNCTIONALS; RAMAN-SPECTROSCOPY; TRANSITION-STATES; GLOBAL SOURCES; CO2 CAPTURE; SULFIDE OCS; ABSORPTION; GEOMETRIES
subject category
Chemistry
authors
Danten, Y; Cabaco, MI; Coutinho, JAP; Pinaud, N; Besnard, M
our authors
acknowledgements
This work was partly developed in the scope of the project CICECO-Aveiro Institute of Materials (ref. FCT UID/CTM/50011/2013), financed by national funds through the FCT/MEC and when applicable cofinanced by FEDER under the PT2020 Partnership Agreement. The authors gratefully acknowledge the support provided by the M3PEC computer centre of the DRIMM (Direction des resources Informatiques et Multimedia Mutualisee, Talence, France) of the New University of Bordeaux and the IDRIS computer centre of the CNRS (Institut du Developpement et des Resources en Informatique Scientifique, Orsay, France) for allocating computing time and providing facilities.